In the Third Generation Partnership Project (3GPP), the fourth generation (4G) cellular network includes a radio access network (e.g., referred to as a long term evolution (LTE) network) and a wireless core network (e.g., referred to as evolved packet core (EPC) network). The LTE network is often called an evolved universal terrestrial radio access network (E-UTRAN). The EPC network is an Internet protocol (IP) packet-switched core network that supports high-speed wireless and wireline broadband access technologies. The EPC network allows user equipment (UEs) to access various services by connecting to the LTE network, an evolved high rate packet data (eHRPD) radio access network (RAN), and/or a wireless local area network (WLAN) RAN. The EPC network is a complex system that includes a number of network nodes that communicate with each other when UEs are accessing the EPC network. An evolved packet system (EPS) is defined to include both the LTE and EPC networks. EPS seeks to improve mobile technology through higher bandwidth, better spectrum efficiency, wider coverage, enhanced security, and full interworking with other access networks.
In the EPC, a policy and charging rule function (PCRF) manages Gx sessions between a packet data network (PDN) gateway (PGW) and the PCRF, and manages Rx sessions between a proxy call session control function (P-CSCF) (e.g., of an IP Multimedia Subsystem (IMS) network) and the PCRF. Gx sessions typically tend to be long-lived sessions. However, the PCRF may experience a Gx session loss due to, for example, software failure, geo-redundancy recovery, etc. associated with the PCRF. The PCRF may also experience a message loss, such as, for example, a reauthorization request being dropped due to overload control, message buffer overflow, etc. During the session loss and/or the message loss, the PCRF and the PGW are unable to synchronize session state (e.g., policy control and charging rules status, quality of service (QoS), event triggers, access point name (APN)-aggregate maximum bit rate (AMBR), etc.). This, in turn, results in a poor user experience when a user is attempting to establish voice and/or video calls. For example, the PCRF cannot process an Rx request for a voice/video call when the PCRF has lost state for a corresponding Gx session. This may require the user to power cycle the UE or to drop and recreate a PDN connection and a Gx connection to establish the voice/video call.